In a boiler generating steam, softened water or ion-exchange water is used as boiler water. According to circumstances, raw water (tap water, industrial water, underground water, river water, lake water, pond water, or the like) is used.
In a boiler steam and condensate system including such a boiler and a metal pipe (for example, a ferrous metal pipe) for distributing steam from the boiler, the steam generated by the boiler cools to be condensed water inside the metal pipe. In the case of condensed water having a higher carbonic acid concentration, the pH thereof decreases to facilitate progression of corrosion of an inside surface of the metal pipe. Progression of corrosion causes metal-loss in the metal pipe, which may lead to a through hole, a crack, and the like.
As Conventional Art 1 to monitor such corrosion of a metal pipe, there has been proposed a method of monitoring corrosion progression in a test piece placed in a test column formed of a transparent material (see Patent Document 1, for example). The method evaluates the corrosion state in a boiler condensate system by passing boiler condensate through the test column containing the test piece, and determining the state of the test piece based on external observation and the corrosion rate.
As Conventional Art 2 to monitor corrosion of a metal pipe, there has been proposed a method by using a boiler condensate system corrosion monitoring device according to an electric resistance method (see Patent Document 2, for example). The method uses a boiler condensate system corrosion monitoring device including a heat exchanger for cooling steam discharged from a boiler into condensed water, a test column to be completely filled with the condensed water and a super-fine metal wire placed in the test column. The method measures the electric resistance of the super-fine metal wire in the test column and evaluates the corrosion state in a boiler condensate system based on an electric resistance change.